Nozzle



Aug. 9, 1960 y B. R. WALSH 2,948,478

NOZZLE I Filed Dec. 24, 1958 INVENTOR.

- BRUCE R. WALSH BY Mak- ATTORNEY NOZZLE Bruce R. Walsh, Pittsburgh,Pa.,:assign'or to Gulf Research & Development Company, Pittsburgh, Pa.,a corporation of Delaware f 1 V Filed Dec. 24, 1958, Ser. mas s- 6Claims; (Cl. 2395-405 The present invention relates to new and usefulimprovements in high-pressure, gun-type burner nozzles, and moreparticularly pertains to a gun-type burner nozzle provided withpassageways communicating between the exterior of the burner nozzle andthe end of the swirl chamber remote from the discharge orifice.Thepresent invention is related to that disclosed in my similarlyassigned application entitled Apparatus filed concurrently with thisapplication, and the nozzle disclosed in this application can includethe discharge orifice construction involving a sharp-edged right angleat the intersection of the swirl chamber with the discharge orificeand/or the substantially cylindrical swirl chamber constructiondisclosed in such other application.

Conventional gun-type burner nozzles, as exemplified in US. Patent Nos.2,321,428 (Schloz) and 2,044,696 (Huss) incorporate structure wherein aninternal nozzle member, commonly referred to as a swirl stem, has afrusto-conical portion that seats flush against a complementary internalsurface of the nozzle body or housing with a swirl chamber definedbetween such portion of the swirl stem and the nozzle body.- Suchconventional structure also comprises a discharge orifice in the nozzlebody communicating withthe swirl chamber and the axial extent of thefrusto-conical portion of the swirl stem' being provided with slotsessentially tangential to the swirl chamber through which fuel enterstheswirl chamber so as to swirl therein and thence pass out thedischarge orifice as a generally conical spray.

Certain difiiculties arise in the use of such conventional structure inthat the rate of fuel flow varies substantially with changes in fuelviscosity resulting in substantial changes in air-fuel ratios withcorresponding variation in combustion efficiency. Also, the dischargeorifice dimensions are so small (particularly with nozzles of low fuelflow rate as are suited for domestic or household use, such nozzleshaving a flow rate in the neighborhood of one gallon per hour) that theperformance of the nozzle is extremely sensitive to coking in thedischarge orifice.

The purposes of the instant invention are to lessen the above-mentioneddifliculties and to improve the combustion of the fuel as indicated bysmoke number (as determined by standard filter test methods) versus theconcentration of carbon dioxide in the combustion products.

Broadly, the present invention involves modifying the previouslydescribed conventional structure by the provision of a passageway in theswirl stem and the nozzle body, such passageway extending from thecenter of the swirl stem adjacent the swirl chamber to the exterior ofthe nozzle body and passing through the seated juncture of the swirlstem and the nozzle body intermediate the slots in the swirl stern.

In a more specific aspect, the present invention involves modifying thepreviously described conventional structure by the provision of an axialblind bore in the end of the swirl stem adjacent the swirl chamber, andthe 2,948,479 Patented Aug. 9, 1960 .2 i I blind bore to the exterior ofthe nozzle body through the juncture of the frusto-conical portion ofthe swirl stem and the nozzle body intermediate the slots in' the swirlstem. I

It has been found that such modification of conventional structure bythe'jprovision of the blind bore and the radial passageways'results inair at atmospheric pressure being induced into the swirl chamber andsubstantially affects the performance of the nozzle. The introduction ofair axially into the end of theswirl chamber remote from the dischargeorifice being additive to the liquid fuel flow rate enables substantialenlargement of the diameter of the discharge orifice relative to thesize thereof necessaryin the absence of such modification; hence thedeleterious clogging effects of foreign matter in the fuel or coking inthe discharge orifice of a nozzle of a particular fuel flow rate can besubstantially reduced. Such introduction of air directly into the centerof'the vortex of swirling fuel in the swirl chamber substantiallystabilizes the fuel flow rate despite large variations in the viscosityof the fuel. 'It has also been found that the further provision ofpassageways extending from. the

combustion efficiency of a conventional and commercial nozzle modifiedby the provision of the air-induction bore and passageways andenlargement of the discharge orifice is substantially improved asmeasured by the smoke number versus the carbon dioxide content of thecombustion products.

The invention will be best understood upon reference to the accompanyingdrawings illustrative of a preferred embodiment thereof, wherein Figure1 is a fragmentary view of a conventional nozzle, modified in accordancewith the invention, showing the nozzle body in central section andshowing the swirl stem in elevation except for a portion thereofadjacent the swirl chamber shown in central section; and wherein Figure2 is an end view of the swirl stem with the passageways communicatingwith the blind bore being shown in dashed outline.

Referring to the drawings, the numeral 10 designates a hollow nozzlebody in which a two piece swirl stem designated generally at 12 isdisposed. The swirl stem 12 includes an insert section 14 screwed intothe nozzle body 10 as at 16, a kerf 18 being provided in the sectionRelative radial movement of the sections 14 and 20 is' limited by theprovision of a cylindrical central stud 24 on the head section 20 thatis received in a central cylindrical opening 26 in the insert section14. The opening 26 is sufficiently larger than the stud 24 to permit alimited amount of radial movement of the head section 20 for a purposepresently to become apparent.

The nozzle body 10 is externally threaded at 28 for threaded connectionto a fuel oil supply conduit 30. The swirl stein 12 is spaced from thenozzle body 10 to define an annular space 32 to which liquid fuel issupplied under pressure from the conduit 30 through a central blind bore34 in the section 14 of the swirl stem 12 and an intersecting transverseopening 36 through section 14 of the swirl stem 12.

The'head section 20 of the swirl stem 12 includes a frusto-conical endportion 38 that seats flush against a frusto-conical internal surface 40of the nozzle body 10. A swirl chamber 42 is defined between thefrustoconical portion 38 of the swirl stem section 20 and the nozzlebody 10, and a discharge orifice 44 is provided in the nozzle body 10communicating with the swirl chamber 42. The swirl chamber 42 can befrusto-conical in configuration, as shown, or it can be of any desired.

configuration, as for example the cylindrical form shown in myapplication filed concurrently herewith. The discharge orifice 44 alongits axial extent includes an intermediate cylindricalsection 46, withthe discharge orifice 44 being outwardly flared, as at 48, from thecylindrical section 46 towards its exit end and flared, as at 50, to asubstantially lesser extent from the cylindrical section 46 towards itsinlet end at the swirl chamber 42.

The frusto-conical portion 38 of the swirl stem section 20 is providedwith a plurality of circumferentially spaced swirl slots 52 extendingalong the axial length thereof that are essentially arrangedtangentially with respect to the swirl chamber 42. The slots 52 can beessentially straight as shown or generally helical in configuration asthose shown in previously mentioned US. Patent No. 2,321,428. Thepurpose of the slots 52 is to provide fluid communication between thespace 32 and the swirl chamber 42 of restricted cross-sectional area andarrangement so that fuel will flow at high velocity into swirl chamber42 and rotate or swirl about the central axis of the swirl chamber 42.Fuel entering the swirl chamber 42 swirls about in the swirl chamber 42and thence passes, while still rotating, through the discharge orifice44 to be emitted from the nozzle as a generally conical spray. The fuelswirling in the swirl chamber 42 constitutes a vortex such that areduced pressure is produced in a central or axial zonal region of theswirl chamber 42 adjacent the center of the swirl stem section 20. Suchreduced pressure is essentially sub-atmospheric and the means foradmitting air to such region will now be described.

The frusto-conical end portion 38 of the swirl stem section 20 isprovided with an axial blind bore 54, that is, a central opening in theend of the swirl stern section 20 that is otherwise closed except to theextent hereinafter mentioned.

A plurality of circumferentially spaced passageways 56 are provided inthe swirl stern section 20 and the nozzle body that extend radially fromthe blind bore 54 to the exterior of the nozzle body 10, such passageWays 56 passing through the juncture or flush seating area of thefrusto-conical portion 38 with the surface 40 of the nozzle body 10intermediate the slots 52. The arrangement is such that the juncture ofthe frustoconical portion 38 with the nozzle body seals the pasageways56 as they extend from one into the other.

The bore or opening 54 can be made in any suitable manner as bydrilling. The passageways 56 can be formed in any suitable manner,preferably by drilling with the swirl stem 12 and the nozzle body 10assembled as shown. The drilling of the passageways 56 need not becompleted with the swirl stem 12 and the nozzle body 10 in assembledrelation, but can be completed after the drill has commenced topenetrate the swirl stem section 20, thereby assuring registry of thedrilled openings upon reassembling the parts. Drilling of passageways 56can be initiated most easily if the nozzle body 10 is given acylindrical configuration 58 in the portion thereof where such drillingis to be commenced. Of course, diametrically opposed passageways 56 canbe drilled in a single operation. The employment of a plurality ofpassageways 56 is preferred as the clogging of one of them would onlypartially impair their function, though a single passageway 56 of largersize could serve substantially as the functional equivalent of aplurality of such passageways 56.

The size of blind bore 54 is, at its entrance, substantially smaller intransverse dimensions than the swirl chamber "42 at the end of thelatter adjacent the swirl stem section 20. This is for the reason thatfuel swirling in the swirl chamber 42 will not be forced into the bore54 by centrifugal force, and so that the bore 54 will communicate solelywith the central region of the swirl chamber 42 of reduced pressure.Such construction assures air entering the center of the fuel vortex inthe swirl chamber 42. Aside from such limitation as to the maximum sizeof the bore 54 at its entrance at the axial extremity of the swirl stemsection 20, the bore 54 and the passageways 56 can be made as large asdesired to reduce the resistance of air flow therethrough commensuratewith preserving the seal of the passageways 56 as they pass between thenozzle body 10 and the swirl stem section 20.

A nozzle according to the invention was made by modifying a standard,commercial, high-pressure, guntype burner nozzle rated at one gallon perhour. Two passageways 56 were provided, each having a diameter of 0.013inch, and a blind bore 54 was provided having a diameter of 0.018 inch.The discharge orifice 44 was enlarged so that the minimum diameterthereof was increased from 0.0105 inch to 0.037 inch. The delivery rateof such nozzle prior to such modification was 0.91, 0.98 and 1.21gallons per hour for kerosene, No. 2 fuel oil, and mineral seal oil,respectively; and was 1.15, 1.11 and 1.16 gallons per hour for suchfuels respectively after modification. Also, marked differences existedbetween the smoke number versus carbon dioxide content of combustionproducts prior to and after modification according to the invention.Comparative tests were made using the unmodified and the modified nozzlein which the conventional blast tube air supply (not shown) was variedto change the carbon dioxide content of the combustion products. Table Ishows the results obtained with the unmodified nozzle, and Table IIshows the re-' sults obtained with the same nozzle modified as specifiedabove in accordance with the invention.

Table 1 Percent carbon dioxide: Smoke number (Bacharach) 8.2 0.55 8.5 a1.4 9.4 2.3 10.0 3.2 10.6 4.8 12.0 6.65

Table II Percent carbon dioxide: Smoke number (Bacharach) 9.5 0.5 10.5 22 11.5 5 5 Comparison of the above tables shows the improved combustioncharacteristics obtained on modifying the conventional nozzle inaccordance with the invention.

Plots of the above data indicate that for a smoke number of 3 (about themaximum tolerable for domestic heating use), the unmodified nozzleyields only 9.85 percent carbon dioxide compared to 10.75 percent carbondioxide for the modified nozzle.

An outstanding advantage of the invention, other than the stabilizationof fuel flow rates, the reduction in the deleterious effects of orificecoking and the improved combustion characteristics obtained, is that theapplication of the principles thereof to existing nozzles can be readilyand simply accomplished. Another major advantage resides in the factthat air is directly introduced into the swirl chamber '42 of the nozzlewithout the use of any special means for forcing air into the swirlchamber 42 being required. It will be understood, of course, that thenozzle of the invention is used in the conventional manner, that is, thesame is concentrically disposed within an air blast tube (not shown),and is therefore exposed to an ambient air pressure slightly in excessof atmospheric air pressure (a few inches of water at most aboveatmospheric); however, such pressure differential tending to favor thedesired induction of air into the swirl chamber 4-2 is incidental tocustomary nozzle use and is not considered to be the result of theprovision of special means for forcing air into the swirl chamber 42.Though the nozzle of the invention does not require the provision ofspecial means for forcing air into the passageways 56 at a faster ratethan would otherwise occur, the provision of special means forsupplementing or increasing the rate of introduction of air into thepassageways 56 is not precluded, and can be employed in conjunctiontherewith if desired.

The two piece construction of the swirl stem 12 yields two importantadvantages, namely, the radial freedom permitted the head section 20aifords greater assurance of the proper alignment of and seating of theswirl stem section 20 in the nozzle body 10, and the rotational freedomof the head section 20 facilitates reassembly of parts of the nozzle sothat the portions of the passageways 56 in the section 20 and the nozzlebody are in registry. It will be noted that the nozzle can be assembledwith a wire or other alignment instrument inserted in one of thepassageways 56 during the time that the swirl stem section 14 is screwedin tight.

The illustrated preferred embodiment of the invention is susceptible tonumerous variations without departing from the spirit thereof. Exemplaryof such changes would be the seating and sealing area of the swirl stemsection 20 with the nozzle body 10 being only an approximation of afrusto-conical surface, or the placing of the swirl slots 52 in thenozzle body 10 rather than in the swirl stem 12.

From the foregoing, the principles of the invention as well as theapplication thereof will be clear to those skilled in the art andfurther description is believed unnecessary. Narrowness of inventivescope is not to be inferred from the detail of the description,attention being directed to the appended claims for ascertainment of theactual scope of the invention.

I claim:

1. In a gun-type burner nozzle, apparatus comprising a hollow nozzlebody having a central axis, the interior of the nozzle body having asubstantially frusto-conical surface adjacent one end thereof that iscoaxial with the central axis, a swirl stem coaxially positioned in thenozzle body having a substantially frusto-conical portion adjacent oneend thereof that is complementary to and seated flush against thefrusto-conical surface of the nozzle body, said one end of the swirlstem being spaced from the nozzle body to define a swirl chambertherebetween, said one end of the nozzle body being provided with adischarge orifice coaxial with the swirl chamber, means defining aplurality of circumferentially spaced slots at the seated juncture ofthe swirl stem and the nozzle body extending along the axial length ofsuch juncture and arranged essentially tangential to the swirl chamber,a passageway extending through the swirl stem and the nozzle body fromthe center of said one end of the swirl stem to the exterior of thenozzle body, said passageway passing through the seated juncture of theswirl stem and the nozzle body intermediate the slots.

2. The combination of claim 1, wherein the swirl stem is comprised of ahead section and an insert section, said sections having flat surfacesin sliding engagement on a plane normal to the central axis.

3. The combination of claim 1, wherein the swirl stem is comprised of ahead section and an insert section, said sections having fiat surfacesin sliding engagement on a plane normal to the central axis, one of saidsections having a central opening, and the other of said sections havinga stud loosely received in said central opening.

4. In a gun-type burner nozzle, apparatus comprising a hollow nozzlebody having a central axis, the interior of the nozzle body having asubstantially frusto-conical surface adjacent one end thereof that iscoaxial with the central axis, a swirl stem coaxially positioned in thenozzle body having a substantially frusto-conical portion adjacent oneend thereof that is complementary to and seated flush against thefrusto-conical surface of the nozzle body, said one end of the swirlstem being spaced from the nozzle body to define a swirl chambertherebetween, said swirl chamber being substantially frustoconical inconfiguration, said one end of the nozzle body being provided with adischarge orifice coaxial with the swirl chamber, the frusto-conicalportion of the swirl stem being provided with a plurality ofcircumferentially spaced slots extending along the axial length thereofand arranged tangential to the swirl chamber, a passageway extendingthrough the swirl stem and the nozzle body from the center of said oneend of the swirl stem to the exterior of the nozzle body, saidpassageway passing through the seated juncture of the swirl stem and thenozzle body intermediate the slots in the swirl stem.

5. In a gun-type burner nozzle, apparatus comprising a hollow nozzlebody having a central axis, the interior of the nozzle body having asubstantially frusto-conical surface adjacent one end thereof that iscoaxial with the central axis, a swirl stem coaxially positioned in thenozzle body having a substantially frusto-conical portion adjacent oneend thereof that is complementary to and seated flush against thefrusto-conical surface of the nozzle body, said one end of the swirlstem being spaced from the nozzle body to define a swirl chambertherebetween, said one end of the nozzle body being provided with adischarge orifice coaxial with the central axis and communicating withthe swirl chamber, the frusto-conical portion of the swirl stem beingprovided with a plurality of circumferentially spaced slots extendingalong the axial length thereof and arranged tangential to the swirlchamber, said swirl stem having a blind axial bore in said one endthereof, and a plurality of circumferentially spaced passagewaysextending radially from the blind bore to the exterior of the nozzlebody through the juncture of the frusto-conical portion of the swirlstem with the nozzle body intermediate the slots.

References Cited in the file of this patent UNITED STATES PATENTS1,639,685 Coffey et a1. Aug. 23, 1927 2,019,815 Holtham Nov. 5, 19352,107,601 Davis Feb. 6, 1938

